It is well known in the electronics arts to manufacture semiconductor devices. Silicon is the most commonly used semiconductor material although other materials are also used. An important aspect of the manufacturer of semiconductor devices is the metallization used to make contact thereto.
Many different metallization schemes are known in the art. Aluminum, gold, titanium, tungsten, copper, and alloys thereof are examples of commonly used metallization materials. Frequently such materials are used in layered combinations in order to achieve properties that are not obtainable with individual materials. Titanium-tungsten (TiW) is a well known barrier and adhesion layer material. Meyer et al. discuss the use of TiW/Au metallization for assembly purposes in a paper entitled "Metallurgy of TiW/Au/Cu System for TAB Assembly" published in J. Vac. Sci. Technol., May/June '85, pp. 772-776. In this reference the chip level metallization is aluminum and the bump metallization is gold. Among other things, Meyer et al. discuss the improvements in the barrier properties of TiW that can be achieved by sputtering TiW in the presence of nitrogen to form a titanium-tungsten-nitride (TiWN), however no attempt was made to use the TiWN. Nowicki et al. has shown that TiWN has improved barrier properties over TiW, in a paper entitled "Studies of Ti-W/AU Metallization on Aluminum", published in Thin Solid Films. Vol. 53, 1978, pp. 195-205. The use of a TiW/TiWN/TiW/Au metallization is discussed. The interdiffusion between aluminum and gold with the TiW/TiWN/TiW as the barrier and adhesion metallization scheme is discussed. Here the two layers of TiW act as adhesion layers to the aluminum layer and the gold layer. TiWN acts only as a barrier layer.
Other applications for TiWN have been discussed in a paper entitled, "Reliability of High Temperature I.sup.2 L Integrated Circuits", by Denning et al., published in IEEE/IRPS Proc., 1984, International Reliabiity Physics Symposium, pp. 30-36. wherein the use of TiWN as a barrier layer and chip interconnection metallization is discussed. Here it was found that TiWN did not adhere well to the wafer oxide or a gold layer.
While these various papers discuss the desirability of using aluminum/TiW/TiWN/TiW/Au metallization sandwiches for interconnection and/or lead attachment purposes on semiconductor devices, considerable problems remain in the preparation of these films in a practical way for volume semiconductor manufacture in order to achieve the theoretically desirable properties. Accordingly, a need continues to exist for improved manufacturing methods for forming sandwich type metallization arrangements utilizing TiW adhesion layers and TiWN barrier layers, particularly in combination with gold, aluminum, copper and other metals of interest in the semiconductor art. Accordingly, it is an object of the present invention to provide an improved metallization process for use in electronic circuits, particularly semiconductor devices and circuits.
Another object of the present invention is to provide an improved metallization process for forming metallization sandwiches employing TiW as an adhesion material and TiWN as a barrier material.
A further object of the present invention is to provide an improved fabrication process for metallization layers utilizing TiW as an adhesion material and TiWN as a barrier material in the presence of a highly electrical conducting outer layer, such as for example gold.